The present invention relates to a fuel feeding aggregate for an internal combustion engine, such as for example electric fuel pump incorporated in a fuel supply system.
An electric motor is for example provided for driving fuel feeding aggregates for internal combustion engines. It is axially connected in alignment with a feed pump and arranged in a joint housing. This is disclosed for example in the German patent document DE 43 31 803 A1. The electric motor has a stator which is arranged in a housing and provided with two alternatingly current-supplied stator coils, in which a rotor non rotatably arranged on a housing-supported rotor shaft is rotatable. The rotor is composed of a support which is guided on the rotor shaft and a magnet segment arranged on the support over the peripheral surface. They are held on the rotor shaft by holding clamps in abutment with the support. The holding clamps are formed so that during the mounting of the individual components of the rotor, they provide centering of the magnet segments, and after the complete mounting all rotor components are clamped so that the magnet segments are held in abutment against the rotor. In the configuration disclosed in the prior art, a check valve is provided in the fuel feeding direction behind the fuel feeding aggregate.
Accordingly, it is an object of the present invention to provide a fuel feeding aggregate for internal combustion engines, which is a further improvement of the existing aggregates.
In accordance with the present invention a check valve is integrated a suction-side end in the housing of the fuel feeding aggregate and maintains a system pressure in the fuel feeding aggregate.
When the fuel feeding aggregate is designed in accordance with the present invention, it has the advantage that the check valve on the electric fuel pump maintains the feeding chamber of the fuel pump sealed relative to the tank.
The sealing of the feeding aggregate relative to the fuel tank acts so that even in the event of long stoppages no gradual idle running of the fuel supply system occurs and it remains filled from the electric fuel pump to the injection valve. Thereby the maintenance of the pressure in the fuel feeding system is prevented, which for example can lead to starting difficulties with the gas bubble formation in hot fuel.
Furthermore, with the inventive arrangement of a check valve, the pressure build up time is substantially reduced and the motor therefore can be started faster. Thereby the exhaust gas emission during the starting phase is significantly reduced.
In accordance with a preferable embodiment of the invention, the check valve is arranged on a rotatable feeding element, such as for example a feeding gear of the fuel feeding aggregate. It is therefore guaranteed that, for example, when the fuel feeding aggregate is formed as an electric fuel pump, its motor chamber can be substantially sealed from pressure losses.
In accordance with a preferable embodiment, the closing element of the check valve cooperates at the suction-side end of the fuel feeding aggregate with an abutment surface, which surrounds the feeding passage for the fuel, while the abutment surface is formed on a housing element.
The closing element of the check valve arranged at the suction-side end of the fuel feeding element can be formed in a manner which is advantageous for manufacture, as a semi-round head which can be guided on a shaft. In addition to the formation of the closing element as the semi-round head, it is also recommended to form the closing element as a spherical body. The spherical body can be enclosed in a spherical cage which forms a housing insert element.
Both the closing element formed as the semi-circular head with the guiding shaft and the ball-shaped closing body, can be formed so that a restoring force acts on them. For example a restoring spring can extend over the shaft of the semi-round head. It presses the semi-round head, with the fuel feeding aggregate stopped, against the abutment surface of the housing element and thereby closes the feeding passage. Similarly, a ball-shaped closing element in the ball cage can be subjected to the action of a spring force. The restoring spring can be supported at one side of the spherical cage, abut against a valve seat of the abutment surface, and thereby reliably close the feeding passage near the feeding element which feeds the fuel.
In accordance with an advantageous embodiment of the present invention, in a fuel feeding aggregate with a check valve integrated at a suction-side end and a pressure-side end, at the suction-side end of the fuel aggregate a check valve is provided with a spherical closing element. In this very expensive variant of a fuel feeding aggregate it is in addition guaranteed. that a pressure reduction in the pressure conduit due to a leakage in the electric fuel pump, for example at the closure cover for the conduit to the injection valve, can be avoided.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.